Prolactin (PRL) is a pituitary hormone and putative neuropeptide with an exceptionally diverse but poorly understood array of behavioral actions. The proposed research will employ the ring dove (Streptopelia risoria) as a model system to explore he physiological mechanisms by which PRL acts in the central nervous system (CNS) and n peripheral target tissues to influence behavioral expression and to determine where he hormone acts in the brain to promote those changes that are centrally mediated. The ring dove is well suited for these studies because 1) a variety of PRL-induced behavioral alterations have been documented in this species, 2) PRL acts at both central, and peripheral sites to evoke these various behavioral changes, and 3) the distribution of PRL-sensitive target cells has been precisely mapped in the ring dove brain. The proposed research would follow up on previous NIMH-sponsored characterization studies to accomplish five specific aims: 1) to define the role of four PRL-sensitive regions within the dove brain in promoting PRL-induced feeding behavior and suppression of gonadotropin secretion (which in turn could have behavioral consequences); 2) to more precisely define the nature of the receptor population(s) within the dove CNS which mediate PRL and growth hormone-induced changes in feeding and gonadotropin secretion by testing the degree to which these hormone actions can be mimicked or blocked by antibodies against purified PRL receptors; 3) To determine whether PRL-induced changes n gonadotropin secretion are due to altered pituitary sensitivity to gonadotropin releasing hormone (GNRH) or altered GNRH secretion; 4) to define the CNS sites of PRL action in promoting parental responsiveness towards young, the specificity of this centrally mediated action, and the role of PRL-induced changes in non-neural target tissues in promoting parental activity; 5) to determine if intracerebroventricular injections of PRL maintain ongoing incubation behavior in mate-separated doves. These studies are preparatory to a future examination of the neurochemical basis of PRL's behavioral action and the role of native dove PRL in promoting functionally significant behavioral changes in this species. Collectively, these experiments should help elucidate the physiological mechanisms underlying the behavioral and neuroendocrine pathologies associated with clinical hyperprolactinemia and will aid in the formulation of general principles underlying protein hormone-behavior interactions.